Retinal transplant successfully restores sight in rats

Scientists have successfully restored vision in blind rats by transplanting fetal retina cells to regenerate neurons in the vision centres of their brains.
Researchers at the University of California, Irvine School of Medicine found that sheets of fetal cells integrated into the retina can generate nearly normal visual activity in their brains. The findings were published Monday in JNeurosci, the Journal of Neuroscience.
“It’s been known that retinal sheet transplants can integrate into the degenerated eyes and allow the animals to detect light,” said Dr. David Lyon, associate professor of anatomy and neurobiology at UCI School of Medicine.
“But, beyond rudimentary light detection it was not known how well the visual system in the brain functioned with the newly integrated retinal transplant.”
They found that neurons in the primary visual processing centre perform as well as neurons in animals with normal healthy retinas.
“These results show the great potential of retinal transplants to treat retinal degeneration in people,” Lyon said. Almost 1.8 million Americans 40 and above are affected by age-related macular degeneration, and an additional 7.3 million with white deposits under the retina are at substantial risk of developing AMD. Diabetic retinopathy is the leading cause of blindness among adults in the US.
The only existing treatments for age-related macular degeneration and retinitis pigmentosa can only help protect existing cells from further damage and won’t work during late stages of disease once these cells are gone.
Retinal sheet transplants have been successful in humans besides animals but their ability to restore complex vision has not yet been assessed.
“Remarkably, we found fetal retinal sheet transplants generated visual responses in cortex similar in quality to normal rats,” said Lyon.
“The transplants also preserved connectivity within the brain that supports potential of this approach in curing vision loss associated with retinal degeneration.”
Three to 10 months after surgery, rats became sensitive to various attributes of visual stimuli, including size, orientation, and contrast.